In manufacturing plants of such as semiconductors and liquid crystals, an automated material handling system (AMHS) is used in which, since fine particulate dust and the like in the air adversely affect the quality performance of products, articles in the manufacturing process (e.g., in the case of a semiconductor product manufacturing facility, semiconductor substrates and glass substrates for liquid crystal displays, glass substrates for photomasks, and intermediate products of articles to be manufactured such as substrates for optical disks) are accommodated in a cassette, and are transported between a manufacturing apparatus and a storage unit such as a stocker or a simplified buffer unit by a transport system in accordance with a manufacturing process (refer to patent document 1). It should be noted that transport systems based on transport vehicles which travel on a track, including an OHT (Overhead Hoist Transport) system and an OHS (Over Head Shuttle) system for transporting an FOUP (Front Opening Unified Pod) by traveling on a track suspended from a ceiling and a transport system using transport vehicles which autonomously travel on a floor, are a mainstream as the transport systems.
In addition, in the automated material handling system, a carrier ID (a barcode, an RFID (Radio Frequency Identification), an infrared communication ID, etc.) which is identification information for identifying the carrier is attached to each of the carriers which are objects to be transported. When the carrier is transferred by a transport vehicle to a manufacturing apparatus or a storage unit, such as a stocker, a buffer stage, and a simplified buffer unit installed in parallel to a transport path, ID read/write units are respectively installed in their loading ports and unloading ports or interface unit portions of the two ports, and the confirmation of the carrier ID and the reading and writing of the carrier ID which is managed are carried out by a controller of the automated material handling system through this ID read/write unit.
For example, patent document 2 discloses a technique in which a wireless communication function connected to a host computer is installed at respective portions of manufacturing apparatuses and storage units, such as stockers, buffer stages, and simplified buffer units, while electronic modules having a wireless communication function and capable of storing predetermined information (identification information) are respectively mounted on cassettes (objects to be transported), and predetermined information is read from or written into the electronic module by wireless communication to thereby manage the cassettes by the host computer.    [Patent Document 1] JP-A-2005-1886    [Patent Document 1] JP-A-9-283595
However, since the ID read/write units are expensive, in the case where the numbers of manufacturing apparatuses and storage units, such as stockers, buffer stages, and simplified buffer units installed in parallel to the transport path are large, there is a problem in that the cost becomes high.
In addition, in the case where the reading and writing of identification information on the object to be transported are performed by using the wireless communication technology, there is a problem in that the setting of installation sites of the wireless communication function is difficult owing to the directivity of the antenna used in the wireless communication technology. Namely, if the object to be transported enters a dead zone in a wireless communicable range (e.g., the object to be transported deviates from a proper position), wireless communication cannot be established, and therefore there is a problem in that the object to be transported and the identification information on the object to be transported cannot be confirmed. At that juncture, to confirm the object to be transported and the identification information on the object to be transported, the automated material handling system must be stopped and the identification information must be manually read from the ID read/write units with respect to all the objects to be transported. In a case where the number of carriers is large, labor and time are involved, and since the production process is stopped for a long time, the productivity of the manufacturing plant is unfavorably affected.